JPH07505538A - Floor cleaning or finishing machine - Google Patents

Abstract

PCT No. PCT/GB93/00118 Sec. 371 Date Nov. 14, 1994 Sec. 102(e) Date Nov. 14, 1994 PCT Filed Jan. 20, 1993 PCT Pub. No. WO93/14684 PCT Pub. Date Aug. 5, 1993.The invention relates to a machine having a carriage for movement on a floor surface. The carriage has structure for rocking the carriage with respect to a floor surface. A workhead assembly is pivotably mounted on the carriage for movement between a first working position and a second rest position. A biasing structure acts on the workhead assembly to move the workhead assembly from one of the positions to the other. Rocking of the carriage allows the workhead assembly to move under influence of the biasing structure from one position to the other position.

Description

[Detailed description of the invention] Floor cleaning or finishing machine The present invention relates to a washing or finishing machine for body surfaces, and in particular is adapted to move over a floor surface. a carriage means carried on the carriage means, a working throat, and a carriage means carried on the carriage means; and a motor configured to drive said work head in use. It relates to such a machine of the type hereinafter referred to as ``C description type''.

Said working head has a brush or pad with means for fixing the brush or pad. may include a docarrier. The motor means drives the brush or pad carrier. a rotating output adapted to carry and hold the carrier in operative contact with the floor surface; Includes power shaft. The motor means is connected to the rotary output shaft or carriage. The pad carrier extends downwardly through the hole formed in the lower end of the shaft. may be carried on the upper surface of the carriage such that it is coaxially carried at the top of the carriage.

The carriage has an upright handle at its rear end to allow the operator to The machine can be moved on the floor, and during this time the motor is used to clean and polish the floor. The working head is driven at high speed for polishing or polishing. A pair of carriages including the rear running wheels of the carriage, which are mounted on an axle towards the rear of the carriage. . When cleaning or finishing work is completed, the motor is switched off and the work head is turned off. To lift the machine off the floor, the machine tilts back so that it is positioned over the rear running wheels. I can get kicked. The machine then performs other required operations while on said running wheels. It can be pushed by the operator to a location or storage location.

Motors are generally heavy and require lifting the motor and work head off the floor and Moving the machinery to such locations requires considerable physical labor. Let's be recognized for what we do. Additionally, the weight of the machine is supported by the working head during use. However, it is undesirable to store the machine in this condition. This is because the weight of the machine is This is because it tends to deform the plan or bat. When using the The brush or pad drives the work head at high speed. Deformation of the lead can cause the machine to become unbalanced, often resulting in unacceptable vibrations. generate. Machines currently available on the market do not allow pads to be removed after using the machine. Remove the plan from the carrier and reinstall the plan the next time it is needed on the machine. It is desirable to

However, to remove the pad, the machine must be is sloped over its rear width or folded down on its sides. machine weight and The volume makes this task somewhat tedious and therefore requires the removal and replacement of pads or brushes. Easy to replace and transport from one location to another with the pad off the floor. An unwashed or unfinished machine is required which provides an improved means of transporting the machine. desired.

According to one aspect of the invention: rocking means for rocking the carriage with respect to the floor; a first working position and a second working position; a working head that moves or is capable of moving the working head to and from its rest position; pivoting means and said operation for moving the working head from one of said positions to another; a pressing means for acting on a working head, the carriage being oscillated on a oscillating means; The working head may be moved from the one position to the other position under the action of the pressing means. Description characterized in that it is configured to be moved or made movable to a certain location. form of machine or provided.

The pressing means is arranged to act between the working head and the carriage. It may be configured to include a spring. ii'i The spring may be a compression spring or a tension spring. It can be done.

In other embodiments of the invention, the carriage means includes a brush housing. bra The housing has an annular bipartite wall and a cylindrical skirt depending from the periphery of the annular wall. including a brush or butt holder that rotates substantially coaxially within this housing. The first is placed so that it rotates. One means for the motor is such that the output shaft is connected to an annular wall. may be carried on the top surface of the housing to extend coaxially downwardly through the central hole. Ru.

The brush housing and motor means are connected to the working head or the first and second positions. the work head so that it can move with it when moving between locations. and may be coupled in a driving relationship. Working head/brush housing/motor set The weight of the three-dimensional object is applied to the pressing hand when the work head is located in one of the positions. This structure can be distributed asymmetrically with respect to the pivoting means so as to form steps. In this case, rocking the carriage on its rocking means reduces the weight of said working head assembly. enabling movement from said one position to said other position under the action of a force.

In the working position, the work head assembly is in working contact with either the work head or the floor. oriented so that the top surface of the brush housing is generally horizontal. Said resting position In the installation, the brush or pad carrier is placed generally transverse to the plane of the floor. Directed. The working head assembly includes means for supporting the assembly in a rest position. This support means should be such that it contacts the floor surface when the working head is in the rest position. Preferably, it comprises one or more casters arranged in a Yes. According to a particularly preferred embodiment of the invention, the working head assembly is mounted on a brush housing. It consists of two casters attached to the outer surface of the ring.

The top surface of the brush housing is for pivoting the working head relative to the carriage means. It can be equipped with the means of The pivot means includes two pieces fixed to the upper surface toward the periphery thereof. These brackets include upright brackets spaced apart by a diameter of Through holes formed in each bracket are arranged opposite to each other in the direction of the pivot axis. can be made to determine.

The carriage means carries two horizontal pivot means for the working head assembly. The chassis may include spaced apart chassis members. The brush housing pivot bracket is One for each arm on a horizontal axis that generally crosses the front and rear directions of the carriage. Once removed, the working spatula 1-assembly can pivot between its working and rest positions. In the latter position, the pad carrier is attached to the carriage. placed in front.

A handle can be used to rock the carriage with respect to the floor. of the present invention According to a particular aspect, the rear shaft constitutes the rocking means, and the carriage is connected to the rear shaft. -F can be swung back and forth. In some embodiments of the invention, the key on the rocking means is Swinging the carriage backwards is caused by the working head assembly being under the action of said pressing means. The brush housing is supported on casters from its working position in its resting position. be able to move to. This machine therefore moves the casters onto the floor surface to be treated. and from above the rear axle, or from the floor onto said caster and rear axle. can.

The suppressing means moves the working head from the one position to the other position. In the rear right position the working head direction assembly is connected to the pivot axis and is placed over-centered with respect to the point of contact between the floor and the The reaction in the caster imparts a moment about the pivot axis and this The moment acts to hold the working head assembly in the other position, This prevents the working head from returning to one position and causes the machine to slide around on the running wheels and casters. Made to be able to be transported on top. However, the working head remains in its rest position. Fixation or retention releasable by a method known to those skilled in the art so as to The means can be provided.

According to one aspect of the invention, the working head assembly is attached to and including a counterweight that is biased from the pivot axis when the body is positioned in a working position; The weight of the work head assembly is distributed asymmetrically with respect to the pivot. machine When the machine is swung backwards over its rear width, the counterweight swings the working head assembly away. from its operating position to its rest position about its axis.

According to another aspect of the invention, a carriage means adapted to move laterally on a floor surface; a liquid collection container carried on said carriage means and in communication with said container; a chamber, a suction pump in communication with the chamber, and a suction pump in communication with the chamber; and has an inlet at the end remote from the chamber, and the inlet is connected to the floor surface. the structure includes a conduit arranged in line with the suction pump or the chamber. The pressure in the bar is reduced and the liquid on the floor is allowed to flow into the conduit through the inlet. and move it along the conduit into the chamber, and place the weight in the chamber. Cleaning or polishing a floor surface adapted to fall into said liquid collection container under the action of force. The goal is to provide a machine that can do this.

This liquid collection container has a base and integrally molded upright front and rear walls. and a box-like structure with side walls. The liquid collection container is open at the top and This opening may be surrounded by a peripheral flange having a smooth top surface.

This container can have a volume of several tens of liters. Therefore, when it is full, this container It will be appreciated that it may weigh on the order of several seven kilograms. Particularly preferred embodiments According to be continuous with the top surface of each liquid collection container or the top surface of the other container so that the carrier It has a shape that is carried on the horn. This is approximately the total volume of liquid collected by the machine. This has the advantage of making it easier to empty the container.

The chamber has a base and integrally molded upright side walls, a front wall and It may be a box-like structure having a rear wall and a top wall. The chamber is a liquid collection container It is preferable to arrange it so that it may sit on the upper surface(s). Chan The base of the bar has one or more holes formed therein. at the base of the chamber The bottom surface is smoothly shaped to match the top surface of the liquid collection container and one or both of the liquid collection container and the chamber are interposed between the liquid collection container and the chamber. The sealing material is arranged such that the

Preferably, the opening at the base of the chamber corresponds to the opening of the liquid collection container.

The chamber also depends from the periphery of each of the apertures formed in the base of the chamber. may include colors that are seated on the base of a chamber or liquid collection container When this collar extends open through a hole formed in the top of the liquid collection container It is possible. The chamber may include an inlet boss and an outlet boss. The exit boss is said to be suction It can be connected to a hose in communication with a pump.

An inlet boss may be connected to the conduit. Hoses and/or conduits are circumferentially Preferably, it is formed of a flexible pipe of circular cross section with reinforcing ribs. Cha The chamber has two inlet bosses, and the conduit has two inlet bosses connected to the inlet bosses. hoses, each hose separated from the chamber. connected to the nozzle at the side.

An inlet boss is formed in the chamber towards its base, and an outlet boss is formed in the chamber towards its base. Preferably, it is placed towards the top of the. According to such a structure, the inlet port The liquid entering the chamber at the source(s) is moved under the action of gravity into the liquid collection container. into) shi, out [cannot enter 1.

The suction pump can be carried on the carriage, preferably near the rear wheel. or 10,000 of them. The machine also contains a liquid containing cleaning or polishing liquid. Including tank. The tank has an integrated bottom wall, front wall, rear wall and top wall. Consists of a molded box-like structure. This tank is a conduit that terminates alongside the floor. Have a roll connected to? Rub. One fruit of this invention! In four cases, this conduit It terminates inside the brush housing lined up with the brush holder. This tank contains fluid. It may have a mouth and a suitable lid. This reservoir is designed to support a liquid collection container. In a preferred embodiment of the invention, the upper wall of this reservoir is a liquid collection container. It is molded to match the bottom wall of the vessel.

According to a particular aspect of the invention, the chamber is hingedly connected to the att handle. , chamber or liquid container - in closed position seated in L and the chamber is said liquid collection container. The chamber can be rotated between the open position and the open position where it is lifted and released. It can be done. liquid collection container(s) when the chamber is in the open position; can be lifted away from the liquid reservoir for emptying.

Baths, liquid collection container(s) and chambers may be made of e.g. polypropylene. molded in a suitable thermoplastic material well known to those skilled in the art, such as I'm going home. At least one of the chamber walls and/or liquid collection container is transparent The contents of the liquid collection container can be inspected to ensure that it is Be able to determine when it needs to be filled and emptied.

Reference is now made to the accompanying drawings, which are given by way of example only and which illustrate how the invention may be carried out. This is an explanation.

In the drawing, FIG. 4 is a schematic side view (partially in section) of a machine according to the invention; Ru.

2 is a second side view of the machine of FIG. 1; FIG.

FIG. 3 is a schematic rear view of the machine of FIG. 1;

FIG. 4 is a sectional view taken along line IV-IV in FIG.

Referring to FIG. 1, cleaning or finishing a floor includes a carriage 12. , this carriage has two horizontally spaced forward chassis parts 18.1 Contains 9. The carriage 12 carries a working head 100 at its front end I5. and this working head pivots about a horizontal axis 117 between said members 18,19. This axis is oriented at right angles to the longitudinal direction of the gear ridge 12. It's been done.

Assembly f: #100 includes brush housing +10, and this brush housing is It includes an annular body 112 with a descending cylindrical scar N14, the annular body 11.2 It carries a motor I24, the housing of which is fixed to the upper surface of the annular body 112. The output shaft of a motor (not shown) passes through the central hole of the annular body 112. It extends downward coaxially. The output shaft has a plate shape at the lower end. A pad carrier (also not shown) is mounted on the housing. It is arranged so as to be coaxially rotatable inside the ring +10. pad carry The brush generally has a circular bottom surface, and this bottom surface is connected to a circular brush or bud unit l-1. 22 for releasably attaching the brush 122, the lower end of the brush 122 is 110 into working contact with the surface on which the machine is placed as shown in FIG. It is made to extend downward.

The motor 124 carries a counterweight 130, which is attached to the motor housing. attached to the outer surface of the rod and extending rearwardly so as to provide a working surface in the first position. The weight of the head assembly 100 is now distributed asymmetrically about the pivot axis 117. has been done.

The brush housing 110 is equipped with pure horizontally spaced casters 132. , and these casters face toward the rear of the outer surface of the housing 110. attached to the caster or the counterweight 130 and the pivot axis 117 It is made to be located on the same side of the

Referring to FIG. 4, the annular body 112 also connects the working head assembly 100 to the member 1 8.19 is provided with two mounting brackets (116). each bra ket 116 has two horizontally spaced upright plays 1-118.119. each plate has a hole 12+ formed toward its upper end. Said bra kets 116 are disposed at the periphery of the annular body 112 diametrically opposite each other; One is attached to each of said members 18,19. Each member 18.19 The part passes between the plates 8 and 19 of the corresponding bracket 116, and The pivot pin 120 or the member 118.11 passes through the hole 121 of the bracket 116. 9, which extends around the pivot axis 117. Work hard! 00 can be pivoted.

FIG. 2 shows the work head assembly 100 moved from the first position by an angle of about 90''. The brush housing 110 is pivoted rearward to the front end 15 of the carriage 12. and between the motor housing 124 and said members 18,19. Working head assembly +00 is shown in a second position adapted to be placed. Ru. The work head assembly 110 is supported on the casters 132 and these keys The caster is rested on the floor in front of the pivot axis +17, which allows the caster to Each of the weight and reaction of the machine at or around the pivot axis of the working head The assembly is maintained in a second or rest position.

The steering wheel I2 has a handle 25 attached to the rear end 15, and the handle The dollar 25 includes an elongated shaft 27 extending upwardly and rearwardly; There is a handlebar 29 attached to the liquid part. The shaft 27 is the mechanical The operator uses the handle to move the carriage 12 relative to the floor with the rear wheels 1 6, thereby raising the front end 15 of the carriage. and also allows the work head assembly 100 to be lifted off the floor. It can be fixed to the carriage 12 in a similar manner. The machine swings like this First, around the pivot axis +17 due to 1tJi of 0 between the work spatula) and the assembly The torque applied to rotates assembly 100 toward its second position. Second In the position , the caster 132 is located below the brush housing +10 and on the pivot axis 11. 7, on which the front end 15 of the machine is supported.

Position the working head assembly of the machine in its second rest position as described herein. When the motor shaft is removed, the pad or bracket attached to the motor shaft holder will be removed. The brush unit is exposed to facilitate maintenance and/or its removal and replacement Let's be recognized. Furthermore, this machine is supported in a second position, thereby providing support for cleaning or finishing the and the floor so that the machine can be easily moved.

In particular, a machine as described herein has a working head assembly in a second rest position; A brush housing extends upwardly and rearwardly from the point of contact between the floor and said caster. Ru.

The upwardly directed reaction acting on the caster is therefore about the pivot axis 117. exerts a torque, which forces the work head assembly into position as the machine is moved across the floor. act to hold it in its rest position.

However, the pivoting between the working head assembly and the carriage means may be fixed or This is provided with locking means for releasably securing said assembly in its rest position. may be modified by any method well known to those skilled in the art.

The floor maintenance machine 10 applies a pad or brush unit to the floor to be treated with cleaning liquid or polishing liquid. 122 is provided with a fluid handling device for supplying water. The device is configured to a first container 40 mounted on the wheel 12 generally above the rear wheel 16; .

The first container includes a generally square bottom wall 42 with an upwardly directed recess 4 4 (see Figure 3).

The bottom wall 42 has two upright side walls 43, a generally square rear wall 46 and a front It is integrally molded with the wall 45, and the front wall 45 has its F half molded. A rearwardly directed recess is formed, and this recess is located when the working head assembly is in the first position. Partially accommodates motor +24 of working head assembly +00 when in working position do. The recess 48 has a rear wall 45A having an arcuate cross section, and this shape Working head assembly 1. around the moving axis +17. Allows unhindered rotation of OO It is a shape to make it. The side walls 43, the front wall 45 and the rear wall 46 are arranged at the upper end. and are interconnected to each other by a top wall 49, the top wall being formed downwardly. The recess 50 has a generally square cross section. forming a peripheral top flat ledge 57.

The first container 40 also has an outlet (not shown) formed at the lowest position of the bottom wall 42. include. The outlet is located inside the brush housing 110 near the pad carriage. connected to the terminating conduit. The first container 40 also includes an inlet and a suitable lid. ing.

Fluid handling devices for machine 10 include two second liquid collection containers 60. - They are similar to each other and are supported side by side on the upper wall 49 of the first container. held. Each of the second containers 60 has a front wall 61, a rear wall 62, and two side walls. It includes a wall 63 and a shaped base portion 64. Said base portion 64 has a narrow bottom wall 6 5 and first front, rear and side walls 66, 67 and 68, respectively; Each of these -1 and extends outwardly to connect with a corresponding wall of the second container. They meet at a circumferential shoulder 69 that exists.

The front wall, rear wall and side walls are interconnected at their upper ends by a top wall 70. the top wall is formed with a generally square center-to-center lower part 1; An inwardly directed peripheral flange 72 is formed having a smooth upper surface 73. Second container 60 is a recess 5 formed in each base portion 64 or top wall 49 of the first container 40; 0 and is arranged so that each bottom wall 65 is seated, and the shoulder The container 69 is seated on the peripheral ridge 51, and the second container 60 is located on the peripheral ridge 51. Adjacent inwardly facing side walls 63 are continuous with each other and face outwardly of the base portion 64. side walls, front wall and rear wall 64, 66 and 67 respectively or side wall of recess 50- 1- to form an interference fit.

The tR2 container 60 supports a chamber 80, which has a generally flat bottom wall 8. 2, the bottom wall of which has two generally square openings 83 formed therein; [183 are each surrounded by a depending peripheral wall 84. The hanging wall portion 84 is 2 is continuous with the inner end of the flange 72 surrounding the corresponding hole 71. Chan The bottom wall 82 of the bar 80 includes side walls 86, a front wall 87, a rear wall 88 and a top wall 89. It is integrally molded with. The rear wall 88 has an opening 90 formed therein. This opening 90 has a hoss 91 attached thereto. Boss 91 has two flexibility are connected to vacuum conduits 92,93.

One of the conduits 92 shown in FIG. It extends downward from the boss 91 and carries an elongated nozzle assembly 94 at its lower end 93. The nozzle assembly is oriented across the carrier (12).

The nozzle 94 includes a depending peripheral skirt 95, which skirt has a plurality of It is formed by flexible bristles of °C. This nozzle assembly 94 is attached to the holding bar -96. The retaining bar is fixed at a distance vertically from the floor. 7/carriage 12 fixed to the handle 94 and close to the lower end of the handle 25 at the other end. fixed at the rear end 14, this structure is fixed when the machine 10 is moved over the floor. The structure is such that the lower end of the bristles 95 sweeps the floor.

Said other conduit (not shown) has an electrically actuated suction at its other end, 't! Connected to bu 97 , this pump has a rear shaft 16 in a recess 44 formed in the bottom of the first container 40. It is attached to the carriage 12 at the top.

In use, the first container 40 is filled with a polishing or cleaning fluid and rides on the running wheel 16 with the working head assembly 100 positioned at the first working position. so that the plan or pad is kept in working contact with the floor surface. done to. The liquid is delivered from the first container 40 through the outlet conduit onto the floor at a predetermined rate. The vat or brush unit 122 is rotated on the floor to remove the polishing agent. Alternatively, it is driven by the motor 124 to perform cleaning.

The suction pump 97 reduces the pressure inside the chamber 80 and the second container 60. The pressure reduction of the floor air, liquids and dirt and other dust and debris is caused by the nozzle assembly 94. position so that it enters the conduit 92. liquid slurry or inside the nozzle 94 and moves upward through the conduit 92 until it reaches the boss 91. liquid part and Any relatively massive particulate matter is then forced by gravity into chamber 80 and It falls through the funnel 71 into the second liquid collection container 60 . air and its Any relatively small mass of dust contained therein is removed along conduit 95 by suction pump 97. It flows up to the point where it is discharged into the surrounding environment. The chamber 80 and the second container 6 The decrease in pressure compared to the atmospheric pressure of 0 is said to cause a mutual attractive force to act between them. This force has the advantageous side effect of forcing the bottom wall 82 of the former against the top wall 70 of the latter. Press down to strengthen the airtight seal between the two.

When the second liquid collection container 60 is full or near full, the suction pump 97 is switched off. is turned off to release the suction force between the chamber 80 and the second container 60. Cha The member 60 is then removed. Second container 60 can then be removed.

The second container 60 is removable separately from the first container 40 so that the latter can be emptied and refilled. I can do that.

In a variation of the invention as described herein, one type of liquid collection container has two separate For example, the latter structure described above can be replaced with the second container 80 attached to each facilitates the task of emptying. This is because each container contains approximately the total weight of the contaminated liquid. This is because only half is required.

Copy and translation of written amendment) Submission (Article 184-8 of the Law of Arrangement) January 1994 ? 5 Condolence circle

Claims (14)

[Claims] 1. a swinging means for swinging the carriage with respect to the floor; a first working position; A work head that moves or is movable to and from a second work position. head pivoting means and for moving the working head from one of said positions to another; comprising pressing means acting on the working head; Rocking the carriage on the rocking means works under the action of the pressing means. moving or making the head moveable from the one position to the other position; A machine of the description type characterized in that it has such a structure. 2. 2. The machine as claimed in claim 1, wherein said pressing means comprises a working head and a housing. characterized by comprising a spring arranged to act between the ridges. machine. 3. A machine as claimed in claim 1 or claim 2, wherein the carriage means comprises a brush. The brush housing includes an annular upper wall and a peripheral edge of the annular wall. This housing includes a cylindrical skirt depending from the brush or pad holder. a machine characterized in that it is arranged to rotate substantially coaxially within a machine. 4. A machine as claimed in any one of the preceding claims, comprising motor means and a brake. The rasp housing is arranged so that the working head moves between said first and second positions. A machine characterized by being able to move together with its working head. 5. A machine as claimed in claim 4, comprising a working head, a brush motor and a shaft. The weight of the housing assembly is distributed asymmetrically with respect to the pivoting means to form said pressing means; The structure allows the carriage to rock on its rocking means under the action of gravity. to enable movement of the working head assembly from said one position to said other position; A machine characterized by being made by 6. A machine as claimed in any one of the preceding claims, wherein the working head assembly is The top surface of the brush housing is generally horizontal with the working head in working contact with the floor. A machine characterized by being oriented so that 7. A machine as claimed in any one of the preceding claims, wherein the working head assembly is means for supporting the assembly in a rest position, the support means being such that the working head is one or more pieces arranged so that they touch the floor when placed in the rest position A machine characterized by comprising upper casters or rollers. 8. A machine as claimed in any one of the preceding claims, characterized in that the surface includes means for pivoting the working head relative to the carriage means; Said pivoting means has two spaced uprights fixed to said upper surface towards its periphery. including brackets arranged diametrically opposite each other. and a through hole formed in each bracket defines the pivot axis. A machine characterized by: 9. 9. The machine as claimed in claim 8, wherein the carriage means is mounted on the working head assembly. including two horizontally spaced chassis members carrying pivoting means for and further characterized in that the pivoting placket on the brush housing is connected to a carriage. one on each arm on a horizontal axis that generally crosses the front and back direction of the allows the working head assembly to pivot between its working and rest positions. and in the latter position the pad carrier is placed in front of said carriage. A machine characterized by: 10. A machine as claimed in any one of the preceding claims, wherein the rear wheel has a swinging means. configured, the carriage can be swung back and forth on the rear wheels, and the hand A machine characterized by being used for swinging the carriage with respect to the floor. Machine. 11. A machine as claimed in any one of the preceding claims, characterized in that the carrier is mounted on rocking means. oscillating the working head assembly under the action of said pressing means position to a rest position supported on said roller means of the brush housing. A machine characterized by being able to move or move. 12. A machine as claimed in any one of the above claims, wherein the pressing means is a work head. characterized in that it operates to move the code from the one position to the other position. and further, the working head assembly has a pivot axis and a shaft between the roller means and the floor surface. arranged over-center with respect to the point of contact, whereby said roller means The reaction at causes a force moment about said axis, which causes the working head assembly to It acts to hold the solid body in said other position, thereby keeping the working head on the floor. A machine characterized by being able to be transported by being released from contact with the machine. 13. 13. The machine as claimed in claim 12, wherein the working head is held in its rest position. A machine characterized in that it is provided with releasable fixing or retaining means so that it can be held in place. 14. A machine as claimed in any one of the preceding claims, wherein the working head assembly is Includes a counterweight that is offset from the pivot axis, thereby providing a working position in the working position. The weight of the head is distributed asymmetrically with respect to the pivot, and this structure , when the machine is rocked backwards onto its rear wheels, the counterweight is attached to the working head assembly. for pivoting about its axis from its operating position to its rest position. Featured machines.